Renáta Górová

Direct silylation of Trypanosoma brucei metabolites in aqueous samples and their GC-MS/MS analysis.

A simple two-step method for the derivatization of polar compounds (lactate, alanine, glycerol, succinate and glucose) using hexamethyldisilazane (HMDS) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) was developed. This method allows direct derivatization of aqueous samples wihout sample pretreatment. The method was used for the analysis of the metabolites of the unicellular organism Trypanosoma brucei. The limits of detection by GC-MS/MS analysis were in the range of 0.02 mg L(-1) for glucose to 0.85 mg L(-1) for lactate.

The analysis of linear and monomethylalkanes in exhaled breath samples by GC × GC-FID and GC–MS/MS

A new arrangement of the INCAT (inside needle capillary adsorption trap) device with Carbopack X and Carboxen 1000 as sorbent materials was applied for sampling, preconcentration and injection of C6C19n-alkanes and their monomethyl analogs in exhaled breath samples. For the analysis both GC-MS/MS and GC×GC-FID techniques were used. Identification of the analytes was based on standards, measured retention indices and selective SRM transitions of the individual isomers. The GC-MS/MS detection limits were in the range from 2.1 pg for n-tetradecane to 86 pg for 5-methyloctadecane. The GC×GC-FID detection limits ranged from 19 pg for n-dodecane to 110 pg for 3-methyloctane.

Equivalent chain lengths of all C4–C23 saturated monomethyl branched fatty acid methyl esters on methylsilicone OV-1 stationary phase

Isomer mixtures of monomethyl branched saturated C7-C23 fatty acid methyl esters (FAME) were prepared by performing a methylene insertion reaction to the straight chain FAME and this study model was completed by using commercially available standards of C4-C7 FAME. The equivalent chain lengths (ECL) of all 220 C4-C23 monomethyl branched FAME on OV-1 stationary phase were measured, achieving an average repeatability of ±0.0004 ECL units. The monomethyl branched FAME was identified by GC on the basis of regularity of the fractional chain lengths (FCL) dependence on the number of carbon atoms (C(z)) of individual homologous series of methyl 2-, 3-, …, 21-FAME. The prediction of retention of the first homologues, having the new position of methyl group beginning at higher carbon atoms number, and analogously for the second, third, fourth, and other members of the homologous series, allowed the dependence FCL=f(C(z)) for the first and subsequent members of beginning homologous of monomethyl derivatives of FAME. The identification was confirmed by mass spectrometry. All of the methyl isomers of FAME, which could not be completely separated by gas chromatography due to having a methyl group in surroundings of the middle of the carbon chain, were resolved by mass spectrometry using deconvolution in a SIM-mode. Measured gas chromatographic and mass spectrometric data were applied for identification of the monomethyl branched saturated FAME in tongue coating.

Determination of sevoflurane and its metabolite hexafluoroisopropanol by direct injection of human plasma into gas chromatography-tandem mass spectrometry.

The developed method for trace analysis of volatile components in plasma allows direct injection of up to 150 samples to the GC-MS/MS system without injector cleaning. This method requires no modification of plasma and the working environment does not interfere with the determination of these analytes. The method allows simultaneous quantification of non-polar sevoflurane and its polar metabolite hexafluoroisopropanol (free, unconjugated form). It is characterized by high repeatability and sensitivity with the detection limit of 0.009 mg L(-1) for sevoflurane and 0.018 mg L(-1) for hexafluoroisopropanol and the linear range 0.050-150 mg L(-1). The method was used to determine the concentration of sevoflurane and hexafluoroisopropanol in plasma samples of 7 patients undergoing general anesthesia with sevoflurane. The average concentration of sevoflurane and free hexafluoroisopropanol was 57.2 mg L(-1) and 0.39 mg L(-1), respectively. The method can be applied for clinical monitoring, as well as for analytical toxicology.

Time-dependent changes in milk fatty acid composition of ewes fed a winter ration supplemented with linseed or sunflower oils.

The effects of adding sunflower and linseed oils to a standard winter ration with a lower concentrate content on the milk fatty acid composition in lactating ewes were investigated. Eighteen dairy ewes randomly chosen from the ewe flock were divided into three groups: the first group was fed a winter ration, the second one a winter ration supplemented with sunflower oil, and the third a winter ration supplemented with linseed oil for a period of 12 days. In the treatment groups, the concentrate was partially replaced by 3.0 g/100 g sunflower or linseed oils. Milk samples were taken daily from morning milking for the analysis of fatty acid composition to determine their temporal daily variations. The responses to sunflower oil compared with linseed oil addition after the end of experi - ment were slightly higher for conjugated linoleic acid (CLA) ( P < 0.05), linoleic acid ( P < 0.001), trans-10 18:1 (P < 0.001), 6:0 to 16:0 ( P ≈ 0.05 - P < 0.001), whereas a higher content of α-linolenic acid (ALA) (3-fold) ( P < 0.001), oleic acid ( < 0.001), and 18:0 (P < 0.001) was found in milk after linseed oil addition. The responses to both oil additions were relatively sustainable with regard to CLA, trans-11 18:1 (vaccenic acid, VA), and ALA content after the last 6 days of supplementation. The winter ration supplementation with sunflower or linseed oil led to a 3-fold increase in CLA milk fat content (0.6-2.0 or 1.8 g/100 g fatty acid methyl esters (FAME), P < 0.001) and a 3-fold increase in VA milk fat content (1.2-3.8 or 4.1 g/100 g FAME, P < 0.001), however the content of trans-10 18:1 was 5-6-fold higher, compared with unsupplemented winter ration. Plant oil supplementation enhanced the total content of CLA, VA, ALA by 5.0 and 3.9 g/100 g FAME ( P < 0.001) for linseed and sunflower oil supplementation, and decreased the total content of 12:0, 14:0, and 16:0 by 9.3 and 5.8 g/100 g FAME ( P < 0.001) compared to winter diet, respectively.

FIA-MS/MS determination of creatinine in urine samples undergoing butylation

Flow injection analysis-tandem mass spectrometry has become widely used for analysis of many biomarkers in various biological matrices. To improve the sensitivity, the compounds are often determined as their butylesters. Since the concentration of urinary excreted compounds are generally reported after normalization to creatinine, the aim of this study was to investigate the possibility of creatinine determination in urine samples which underwent butylation. The impact of derivatization on urinary creatinine determination was investigated by measuring of underivatized and derivatized samples. The 10% creatine to creatinine conversion was observed during butylation, what above 700 μmol creatine/mmol creatinine caused significant creatinine overestimation. In that case, correction for creatine conversion rate was done. QC samples at six concentration levels were examined and precision and accuracy values fulfill the European Medicine Agency validation requirements. The elaborated method was applied for determination of creatinine in 41 real human urine samples. Determined creatinine concentrations were in the range of 0.27-22.3 mmol/L, linearity was confirmed within the concentration range of 0.27-31.7 mmol/L. Obtained results highly correlated with routinely used enzymatic assay for all tested samples and proposed method provide reliable determination of creatinine in butylated urine in a single run with butylesters of other analytes of interest.

Theoretical and experimental study of recycle capillary gas chromatography with carrier gas propelled by a peristaltic pump

A new technique of recycle capillary gas chromatography (RCGC) characterized by a very high separation efficiency of more than 10(6) theoretical plates has been developed to solve the problem of separation of isomers with similar physico-chemical properties. The technique replaces the recycle valve by a peristaltic pump that propels the carrier gas. A general model has been developed for description of RCGC characteristics and experimentally verified on the retention behaviour of methane and the separation of a test pair of 3-methyl-1-butene and 2-methylbutane.

Analysis of triglycerides in butter, plant oils, and adulterated butter with LPGC-MS

This work is focused on the detection of butter adulteration by sunflower and rapeseed oils using low pressure gas chromatography mass spectrometry (LPGC-MS). The method is based on simple dissolution of triglycerides from butter samples in chloroform and their direct analysis with LPGC-MS. The method allows the detection of characteristic triglycerides as butter adulteration markers and their quantification in different samples, with the possibility to quantify plant oil addition to butter at 0.45% level (using m/z = 600.4 for rapeseed oil) and 0.15% for sunflower oil (using m/z = 598.4). Ten different commercial butters were tested for the presence of sunflower and rapeseed oil. Interestingly, the addition of rapeseed oil up to 1.2% was recorded in one butter brand.Graphical abstract

Peptide-catalyzed stereoselective Michael addition of aldehydes and ketones to heterocyclic nitroalkenes

Stereoselective Michael addition of enolizable carbonyl compounds to a furane-derived nitroalkene was catalyzed by di- and tripeptide organocatalysts. The most competent catalysts were tripeptides possessing Pro–Pro–Glu structure. With aldehydes, Michael adducts were obtained in high yields and with medium-to-high diastereo- (up to 13:1 d.r.) and enantiomeric purities (up to 99% ee). The reaction was less stereoselective with cyclic ketones than with aldehydes.Graphical abstract

Natural Resources and Waste Products in Aquatic Media Remediation and Diclofenac Uptake

Environmental requirements are becoming of great importance in today ́s society since there is an increased interest in the industrial use of renewable resources. For this reason, the objective of the work presented was to examine and compare several natural, commercial or even waste products in diclofenac uptake, using synthetic water solutions in laboratory measurements. Diclofenac belongs to a class of drugs that provides analgesic, antipyretic and anti-inflammatory effects. To date, more than 200 different pharmaceuticals alone have been reported in river waters globally. According to the monitoring provided by the national water authorities and researchers, consumption of pharmaceuticals in the Czech and Slovak Republics are among the highest in Europe. According to our research, the results of the most effective adsorbents in diclofenac uptake from aqueous solutions were products in the following order: Chezacarb, with a capacity nearly 300 mg/g, Peatsorb CB18, with a capacity close to 250 mg/g, the German Silcarbon and the commercial product KlinoCarb, from the company Zeocem, with a capacity of ca. 200 mg/g. The domestic product KlinoCarb, which proved to have sufficiently high adsorption towards diclofenac, including a favourable price, was characterized by H-C CP MAS NMR, Raman spectroscopy, XRD, and moreover, as with the other materials studied, by the SEM and S(BET) methods. A R T I C L E H I S T O R Y Received: April 26, 2018 Revised: May 29, 2018 Accepted: June 14, 2018 DOI: 10.2174/2213346105666180622125344